First-principles investigation of Rb2Tl(As/Bi)I6 for green technology

Abstract

Rb2Tl(As/Bi)I6 are predicted to be good photovoltaic and thermoelectric materials. In this article, we have carried out firs-principles investigation on structural, electronic, optical and thermoelectric properties of Rb2Tl(As/Bi)I6. The obtained negative formation energy along with absence of imaginary frequency in phonon dispersion curve demonstrated the thermodynamic stability of Rb2Tl(As/Bi)I6 . Also, the obtained electronic band structure with new mBJ functional showed the band gap values of 1.05 eV and 1.63 eV for Rb2TlAsI6 and Rb2TlBiI6, respectively. In addition, the out shining optical properties such as higher order (105 cm−1) of absorption coefficient, appreciable optical conductivity and low reflectivity of Rb2Tl(As/Bi)I6 are resulted from the dispersed direct band gap with suitable values of Rb2Tl(As/Bi)I6. Furthermore, ultra-low thermal conductivity and high electrical conductivity leads to higher ZT values of titled systems. Thus, Rb2Tl(As/Bi)I6 are emerging photovoltaic and thermoelectric materials.

Keywords

• Double perovskite
• Photovoltaic cell
• Optical properties
• Absorption coefficient
• Thermoelectric